changes as per comments

samples/snippets/src/main/java/com/example/spanner/CopyBackupSample.java

@@ -34,25 +34,6 @@
 import java.util.concurrent.TimeUnit;
 
 public class CopyBackupSample {
-  public static void main(String[] args) {
-    if (args.length != 4) {
-      throw new IllegalArgumentException(
-              "Invalid number of arguments. "
-                      + "Usage: CopyBackupSample "
-                      + "<project-id> <instance-id> <source-backup-id> <destination-backup-id>");
-    }
-    String projectId = args[0];
-    String instanceId = args[1];
-    String sourceBackupId = args[2];
-    String destinationBackupId = args[3];
-
-    try (Spanner spanner =
-                 SpannerOptions.newBuilder().setProjectId(projectId).build().getService()) {
-      DatabaseAdminClient databaseAdminClient = spanner.getDatabaseAdminClient();
-      copyBackup(databaseAdminClient, projectId, instanceId, sourceBackupId, destinationBackupId);
-    }
-  }
-
   static void copyBackup() {
     // TODO(developer): Replace these variables before running the sample.
     String projectId = "my-project";
@@ -87,12 +68,12 @@ static void copyBackup(
 
     // Initiate the request which returns an OperationFuture.
     System.out.println("Copying backup [" + destinationBackup.getId() + "]...");
-    OperationFuture<Backup, CopyBackupMetadata> op =
+    OperationFuture<Backup, CopyBackupMetadata> operation =
           databaseAdminClient.copyBackup(
                   BackupId.of(projectId, instanceId, sourceBackupId), destinationBackup);
     try {
       // Wait for the backup operation to complete.
-      destinationBackup = op.get();
+      destinationBackup = operation.get();
       System.out.println("Copied backup [" + destinationBackup.getId() + "]");
     } catch (ExecutionException e) {
       throw (SpannerException) e.getCause();
@@ -114,7 +95,7 @@ static void copyBackup(
                               destinationBackup.getProto().getVersionTime().getSeconds(),
                               destinationBackup.getProto().getVersionTime().getNanos(),
                               OffsetDateTime.now().getOffset())));
-    return null;
+    return;
   }
 }
 // [END spanner_copy_backup]

samples/snippets/src/main/java/com/example/spanner/SpannerSample.java

@@ -95,7 +95,6 @@ public class SpannerSample {
 
   /** Class to contain singer sample data. */
   static class Singer {
-
     final long singerId;
     final String firstName;
     final String lastName;

samples/snippets/src/test/java/com/example/spanner/SpannerSampleIT.java

@@ -17,6 +17,7 @@
 package com.example.spanner;
 
 import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.assertTrue;
 
 import com.google.cloud.Timestamp;
 import com.google.cloud.spanner.Backup;
@@ -328,9 +329,8 @@ public void testSample() throws Exception {
               "Backup %s on database %s pending:",
               backupId.getName(),
               dbId.getName()));
-      assertThat(out).contains(
-              "Copy Backup Operations"
-      );
+      assertTrue("Out does not contain copy backup operations", out.contains(
+              "Copy Backup Operations"));
     } catch (SpannerException e) {
       assertThat(e.getErrorCode()).isEqualTo(ErrorCode.INVALID_ARGUMENT);
       assertThat(e.getMessage()).contains("Cannot evaluate filter expression");